During the past several years, environmental pollution concerns have led those active in the coatings, castings and moldings arts to develop various curable compositions in which organic solvents derived from petroleum have been eliminated or at least substantially minimized. Thus, compositions such as water-based compositions and high solids compositions have been extensively investigated. Even more recently the high cost and scarcity of petroleum by-products has engendered interest in the development of curable compositions which are composed entirely of, or at least substantially of, inorganic components.
Inorganic coating compositions based on alkali metal silicates are well known in the art. Such compositions can be applied from an aqueous medium alone or in combination with various known insolubilizing agents. The insolubilizing agents aid in the fast formation of a water-resistant silicate coating. The coatings are inorganic in nature with the consequent advantages discussed above and possess a desired set of properties.
Unfortunately, pigmented coatings based on the alkali metal silicate can have a less than desired appearance due to an inadequate pigment dispersion in the coating composition. This inadequate pigment dispersion is most noticeable in lapped areas, where fresh additional coating composition is applied over a first coat of the same composition.
The present invention relates to pigmented inorganic coating compositions based on water-soluble or water-dispersible silicates which are capable of providing coatings having good color uniformity.
As used herein, all percents and ratios are by weight unless otherwise indicated.